Buying AR upper, is headspace an issue?

[z7]

I am wanting to buy a new complete upper or two and most of those that are currently in stock do not have a BCG, so I will need to buy a BCG separate.

I will most likely buy from Palmetto State Armory. I know I should have the headspaced checked, but how often, if ever, have you had a problem with AR15 headspace when piecing together a rifle, particularly these "lego sets" from PSA or similar companies.

thanks

 

[RX-79G]

ARs headspace on the barrel extension, not the upper. The upper is pretty much just a tube that keeps the carrier running in a straight line.

 

[z7]

RX, yes you are correct they headspace off of the barrel extension. I am wanting to buy a complete upper (OP edited) like:
http://palmettostatearmory.com/psa-...eedom-upper-with-bcg-and-charging-handle.html

when I buy a BCG for this barreled upper, should I expect headspace issues?

 

[cfullgraf]

While the machining tolerances of the manufacturers between the barrel extension and the bolt is pretty good, it is still a good idea to have the bolt matched to the barrel.

Many will say it is not necessary, but it is quick and easy and good insurance.

If the vendor won't match the bolt and barrel and you plan on buying several uppers over time, the headspace gauges are not too expensive and you can check the bolt yourself.

You would need a go gauge and a no-go gauge. If you want to check the wear on your chamber later, also get a field gauge as well.

 

[desidog]

when I buy a BCG for this barreled upper, should I expect headspace issues?

No, I wouldn't worry about it for a moment. Everything's CNC machined these days, which takes out the human error... As a rule of thumb, i think if you pair a bolt and a barrel and don't use an old bolt on a new barrel or visa-versa, everything should be fine.

 

[Varminterror]

Thousands upon thousands of AR's are built every year without anyone ever checking their headspace - whether built in someone's garage or in a factory. I'd be prone to bet most military contract rifles are not checked before they're shipped out.

It's good to check, and cheap. Don't buy a set of gauges, but pay a local smith $10 to check it for you.

If you have a set of calipers and a headspace arbor, you can use an empty case as a headspace gauge (or even loaded rounds, frankly). Place tape on the case head to increase dimension to match a go-gauge, then add more to replicate a no-go gauge. Pull the bolt from the carrier, remove your ejector, and chamber the round. If the lugs lock up on a go-gauge length, great. If they don't, then no good. If they lock up on a no-go length, no good.

 

[MachIVshooter]

I've assembled a lot of ARs, never seen a headspace issue.

As a rule of thumb, i think if you pair a bolt and a barrel and don't use an old bolt on a new barrel or visa-versa, everything should be fine.

It's a bit overstated, but parts do wear into each other, so it's a good idea to use a new bolt with a new barrel if there is a decently high round count. That said, new bolts are used in high round count barrels all the time after a lug failure or the tail breaking at the cam pin with no problems.

 

[PowerG]

Thousands upon thousands of AR's are built every year without anyone ever checking their headspace - whether built in someone's garage or in a factory. I'd be prone to bet most military contract rifles are not checked before they're shipped out.

It's good to check, and cheap. Don't buy a set of gauges, but pay a local smith $10 to check it for you.

If you have a set of calipers and a headspace arbor, you can use an empty case as a headspace gauge (or even loaded rounds, frankly). Place tape on the case head to increase dimension to match a go-gauge, then add more to replicate a no-go gauge. Pull the bolt from the carrier, remove your ejector, and chamber the round. If the lugs lock up on a go-gauge length, great. If they don't, then no good. If they lock up on a no-go length, no good.

100% (all weapons) min/max headspace checks are required after the HP test per MIL–DTL–71186A. For First Article and Conformance Lot examples the requirement is (a cycle is 120 rounds, for a 6000 round function test):

"3.6.7.6 Endurance headspace measurement. Headspace for weapons being fired with 30 round magazines shall be measured and recorded at the beginning of the test and at the completion of the 50th cycle. After the 50th cycle, the headspace shall not be more than .0028 inch greater than the initial measurement and shall not exceed .0024 inch over maximum (1.4706 inches when measured to the 0.330 inches datum diameter on the first shoulder of the chamber)."

I'd pay the smith rather than trust the tape method.

 

[Jackal]

Should you? Technically yes. Will you ever encounter an issue by not doing so? Highly, highly unlikely.

 

[Taurus 617 CCW]

I used to work for an AR-15 manufacturer. It was the kind that one or two guys built the entire gun from start to finish. Headspace can vary from lot number to lot number of barrels and BCG's. It all has to do with how sharp the chamber reamer is and how deep it was reamed. Within the same lot number of barrels I have seen the headspace vary as much as two gauge sizes when checking different BCG's. We used the 11 gauge set from Forster. The "Go" and "No-Go" gauges have a fairly wide range of tolerance. If your barrel/bolt combination falls within that, you are fine. It is highly recommended to check headspace if doing a virgin assembly from non matched components. A set of gauges runs about $60 and is well worth the price if you plan on doing multiple builds. You can rent gauges for about $7.00 plus S&H. I have used these guys before and have had good experience.
http://www.reamerrentals.com/Default.asp

If you only plan on doing one virgin build then I would take it in and have it checked. Hope that helps.

 

[boom boom]

You can get the vendor to give you a headspaced barrel/bolt combo in normal times if you ask for it--in fact, if you are buying parts from the same source, that should be asked from them but given that the elections has ginned up interest that may not be so.
Otherwise, either rent a headspace gage but use it properly by removing the ejector (it is a real pain to remove the ejector unless you have a magic bolt tool). Field gages are strictly for worn barrel combos and your brass may have a shorter life. Usually go gages are somewhat useful but can be skipped in a pinch if you have a proper dummy round (not a live round). At the very least, you need a no-go gage. You do not need at all the 11 gage set unless you are dealing with match rifles.